Engine body construction of a chain saw

ABSTRACT

In the construction of an engine body of a portable chain saw, a crank case, fuel tank and a lubricating oil tank are made integral. At least a part of the outside of the crank case is surrounded by the lubricating oil tank, and at least a part of the circumference of the latter is surrounded by the fuel tank. A partition wall between the crank case and the lubricating oil tank is provided with a double wall construction having therein a space which opens at either one or both sides thereof, whereby cooling air may be drawn through the inside of the space.

United States Patent [191 Kobayashi et a1.

[54] ENGINE BODY CONSTRUCTION OF A CHAIN SAW [75] Inventors: Torao Kobayashi, Tokyo; Hiromasa Miyata, Mitaka, both of J apan [73] Assignee: Kioritz Corporation, Tokyo, Japan [22] Filed: Sept. 24, 1971 [21] Appl. No.: 183,346

[52] US. Cl. ..l23/41.31, l23/4l.7, 123/122 E,

123/136, 123/195 R, 143/32 [51] Int. Cl. ..F01p l/06, F02f 7/00 [58] Field of Search ..123/l95 R, 195 C,

123/195 P, 198 E, 122 E, 179 SE, 44.31, 41.7,136; 143/32; 74/606 [56] References Cited UNITED STATES PATENTS 3,036,566 5/1962 Dobbertin ..123/l98 E 3,372,679 3/1968 Aitken ..l23/l36 1 May 22, 1973 1 3,561,414 2/1971 Schou ..123/l36 FOREIGN PATENTS OR APPLICATIONS 651,976 11/1962 Canada 143/32 206,748 8/1966 Sweden ..143/32 Primary ExaminerAl Lawrence Smith Att0rneyKarl W. Flocks [57] ABSTRACT In the construction of an engine body of a portable chain saw, a crank case, fuel tank and a lubricating oil tank are made integral. At least a part of the outside of the crank case is surrounded by the lubricating oil tank, and at least a part of the circumference of the latter is surrounded by the fuel tank. A partition wall between the crank case and the lubricating oil tank is provided with a double wall construction having therein a space which opens at either one or both sides thereof, whereby cooling air may be drawn through the inside of the space.

1 Claim, 2 Drawing Figures PATENTEU HAYZ 2 I973 SHEET 2 [1F 2 1 ENGINE BODY CONSTRUCTION OF A CHAIN SAW BACKGROUND OF THE INVENTION This invention relates to an improvement of the construction of the engine body of a portable chain saw, and more particularly to the construction of the engine body of a portable chain saw in which the overheating of a fuel tank is prevented to ensure the smooth running of the engine.

Since a portable chain saw has, in general, relatively a large output for its small size, the calorific value of the engine is large as much. Because of its small size, the heat generated through the calofication is liable to be transmitted to various portions of the chain saw adjacent to the engine. Accordingly, the temperature at those portions is likely to rise abruptly. Particularly in the event that the temperature at the fuel tank rises, the fuel therein is overheated, which results in malfunction of the engine.

Under the conventional disposition as described above, it has been required to prevent the overheat of the fuel tank in the above kind of portable chain saw.

SUMMARY OF THE INVENTION In accordance with the presentinvention, there is provided an improved construction of an engine body of a portable chain saw wherein a crank case of the engine, a fuel tank and a lubricating oiltank are made integral, at least a part of the outside of the crank case being surrounded by the lubricating oil tank, at least a partof the circumference of the lubricating oil tank being surrounded by the fuel tank.

In accordance with the present invention, there is provided an improved construction of an engine body of a portable chain saw wherein a crank case of the engine, a fuel tank and a lubricating oil tank are made integral, at least a part of the outside of the crank case being surrounded by the lubricating oil tank, at least a part of the circumference of the lubricating oil tank being surrounded by the fuel tank so that adirect heattransmission from said crank case to said fuel tank may be shielded by said lubricating oil tank, a partition wall between said crank case and said lubricating oil tank being provided with a double wall construction having therein a space which opens at either one or both sides thereof whereby cooling air may be drawn throughthe inside of said space.

The primary object of the present invention as summarized above isto provide an engine body constructio n of a chain saw which the heat generated at the engine is prevented from transmitting directly to the fuel tank by the intervention of a lubricating oil tank between the engine and the fuel tank, whereby the temperature rise in the fuel tank is suppressed and the running of the engine is made normal and smooth.

Other objects,features andadvantages will be made apparent'from the description of the preferred embodiment described hereinbelow withreference to the accompanying drawing.

BRIEF DESCRIPTION or rn DRAWING and FIG. 2 is a cross sectional 11-11 of FIG. 1.

DESCRIPTION o 'THE PREFERRED EMBODIMENT j view taken along the line trifugal clutch 14. The other end of the crank shaft 13' is provided with a cooling fan 17 fixed thereto and further with a starting device 16. In the drawing, the reference numeral 11 indicates a spike, 19 indicates a throttle lever, 20 indicates a stopping button for the throttle lever 19, and 18a and 18b indicate handles, respectively.

In the present invention, as shown in the embodiment illustrated, a crank case 2 is made integral with a lubricating oil tank 4 and a fuel tank 7 by casting. Further, the outer wall of the crank case 2 serves as the inner wall of the lubricating oil tank 4.. The lubricating oil tank 4 is surrounded by a fuel tank 7. The engine body housing including the crank case 2, the lubricating oil tank 4 and the fuel tank 7 is composed of two divisions dividable by a plane extending parallel to the axis of the crank shaft 13.

The reference numeral 6 indicates an inlet port for the lubricating oil, and 8 indicates an inlet port for the fuel. The lubricating oil in the lubricating oil tank 4 is sent to various portions to be lubricated in the chain saw by an oil supply 15 through a lubricating oil inhaling hose 5.

Further, the boundary wall construction of the crank case 2 and the lubricating oil tank 4 is made of a double wall construction as shown in FIG. 1, so that cooling air may be drawn through the space 2a between the two walls of the double wall construction. Although said cooling air may be naturally drawn, this air, if necessary, is forcibly drawn by means of fan means such as an engine cooling fan as indicated by the numeral 17. By sending air blown into the space 2a by the fan 17 to cool the crank case, the heat transmission from the crank case to the fuel tank through the lubricating oil tank can be effectively shielded.

Furthermore, by mounting a piece of proper heat insulating material (not shown) to the surfaces 4a and 7a of the lubricating oil tank 4 and the fuel tank 7 opposite to the cylinder, the insulation of the heat transmission to the tanks can be further improved.

The heat generated from the engine 1 is distributed over the crank case with the maximum distribution on the cylinder head. The cylinder head is cooled by cooling air blown off by an engine cooling fan 17. On the crank case side of the engine, the outer side of the crank case wall may be effectively cooled by the cooling air that is continuously drawn through the above space in the double wall construction, and thus the heat-transmission to the lubricating oil tank may be limited to that extent. Although some part of the heat transmitted to the lubricating oil tank is accumulated in and warms the oil, a further heat transmission from the oil tank to the fuel tank 7 may be kept minimal so that the fuel in the fuel tank is effectively prevented from being abruptly heated.

In spite of the above steps of transmission of the heat, it should be understood that the fuel will finally by heated to the temperature as high as the crank case after a long time of driving of the engine.

However, in practical use, the chain saw is not continuously driven for such a long time, but intermittently operated. Further, the amount of fuel and lubricating oil is limited to a comparatively small one, and accordingly, new fuel and oil is replenished after relatively a short time of driving. Therefore, the control of the heat transmission by the construction of the body housing is very effective to prevent the overheat of the fuel of the chain saw.

What is claimed is:

1. An engine body construction of a chain saw comis surrounded by said fuel tank so that a direct heat-n transmission from said crank case to said fuel tank may be shielded by said lubricating oil tank, a partition wall between said crank case and said lubricating oil tank is provided with a double wall construction having therein a space which opens at either one or both sides thereof, whereby cooling air may be drawn through the inside of said space. 

1. An engine body construction of a chain saw comprising a crank case of an engine, a fuel tank and a lubricating oil tank, wherein said case, said fuel tank and said lubricating oil tank are made integral with each other, at least a part of the outer side of said crank case is surrounded by said lubricating oil tank, and at least a part of the circumference of said lubricating oil tank is surrounded by said fuel tank so that a direct heat-transmission from said crank case to said fuel tank may be shielded by said lubricating oil tank, a partition wall between said crank case and said lubricating oil tank is provided with a double wall construction having therein a space which opens at either one or both sides thereof, whereby cooling air may be drawn through the inside of said space. 